Ian’s Bird of the Moment – Greater Rhea

Back to South America this time for a flightless Ratite, the Greater Rhea (Birdway: Greater Rhea), a species I was very keen to photograph. Later we’ll consider the other southern continents in the context of the eclectic collection of species that make up the other (mostly) flightless Ratites such as the Ostrich and the Emu.

The Greater Rhea, the largest and most widespread of the three Rhea species in South America, wasn’t numerous in the Pantanal and seemed to be confined mainly to the drier parts of the northern part. However, they weren’t hard to see and we usually saw them in pairs. They were much bigger than I’d expected, like smallish Emus. I’d seen a photo long ago of Rheas running through the pampas of Argentine at speed and appearing, I though then, closer to the size of bustards. Greater Rheas are 127-140cm/50-58in in length and weight 20-25kg/44-55lb, compared with Emus at 150-190cm and 30-55kg, and Australian Bustards at 90-120cm and 3-8kg.
Considering they’re not closely related, I was surprised at how like Emus they looked, though with more delicate features and larger fluffier feathers, more like feather boas than the shaggy, old sheep fleece look of Emus (see the fourth photo). The Greater Rhea is quite widespread through central South America east of the Andes with a range comprising Brazil south of the Amazon Basin, eastern Bolivia, Paraguay, Uruguay and a big chunk of northern and eastern Argentina.
There are two or three species of Rhea. In southern Argentina and neighbouring areas of eastern Chile, the Greater Rhea is replaced by the Lesser Rhea (Rhea pennata) 90-100cm and 15-25kg. Maybe the photo that I had seen long ago was, on second thoughts, of members of this species. The third candidate, the Puna Rhea (Rhea pennata tarapacensis or Rhea tarapacensis), is similar to the Lesser Rhea, also 90-100cm and 15-25kg, perhaps conspecific. It replaces the Lesser and Greater Rheas in northwestern Argentina, northeastern Chile, southwestern Bolivia and a small area of southeastern Peru. Both the Lesser and Puna Rheas have brown feathers on the back with white edges which give them an attractive scalloped appearance.
Back in Australia, the Emu (Birdway: Emu) has a widespread distribution through mainly on the mainland. Only the mainland race survives, other forms, usually now considered races rather than full species, having been hunted to extinction since European settlement in Tasmania, King and Kangaroos Island. The mainland race has been successfully introduced to both Kangaroo Island and Maria Island off the east coast of Tasmania.
Australia and New Guinea have three species of the rather different but related and also flightless Cassowary, with the Southern Cassowary (Birdway: Southern Cassowary) being the only one occurring in Australia.The Cassowary photo shows a watchful father taking his confident child for a walk along the beach as a change from the usual habitat of tropical rainforest in northern and northeastern Queensland. Interestingly in most species of Ratite, the males alone incubate the eggs and take care of the young, with the only exceptions being the Ostriches and some species of Kiwi, where the sexes share parental duties.
The largest surviving Ratites are the Ostriches, Common and Somali, widespread throughout Africa and formerly also in Arabia, Syria and Iraq. The larger males can reach 2.75m/9ft in length and a hefty 156kg/344lb in weight. Common Ostriches are bred widely for their meat and plumage, and feral populations exist in South Australia and beyond their original range in southern Africa.
Early theories of the evolution of these fairly similar species is that they evolved from a small flying ancestor on Gondwanaland that survived the Cretacious-Paleogene mass extinction about 66 million years ago and took advantage of the space left by the extinction of herbivorous dinosaurs by becoming large and flightless before the evolution of large mammalian predators. Parrots, incidentally, share a similar mainly southern distribution and appear to have originated in Gondwanaland, though their subsequent radiation through continental drift was naturally aided by being able to fly.
Needless to say, the story is more complicated than that. Extinct giant members of the group included the Elephant bird of Madagascar and the Moas of New Zealand and there are early ratite-like fossils from the Northern Hemisphere. Existing members include the fowl-like Tinamous of Central and South America which can fly, if reluctantly. The name Ratite comes from the Latin ratis, meaning raft, referring to the flat, keel-less sternum of the flightless species but Tinamous have a keeled sternum. They were formerly excluded from the Ratites but recent genetic studies have confirmed their membership. A better skeletal feature is the unusual, perhaps primitive, palate shared by all of them, which gives the name Palaeognathae, or paleognaths meaning ‘old jaw’ in Greek to distinguish them from the other clade the Neognathae, ‘new jaw’, comprising all other extant species of birds.
This “cladogram” shows the current understanding of the evolution of the Palaeognathae. The apparent close relationship between the Tinamous of South America and the Moas of New Zealand and the Kiwis of New Zealand and the Elephant birds of Madagascar is truly a biogeographers worst nightmare, worse than the unresolved mystery of the related flightless Kagu of New Caledonia (Birdway: Kagu) and the Sunbittern of South America (Birdway: Sunbittern), which we’ve considered before (Bird of the Moment #591). Other complications are the two- rather than three-toed feet of Ostriches and the dagger-like inside toe of Cassowaries.
One solution is to propose that flightlessness evolved in parallel perhaps five times in different parts of the world as this is easier to contemplate that the independent re-development of flight in Tinamous from a flightless ancestor. Loss of flight has occurred fairly readily in other groups such as the Dodo and flightless rails, particularly on islands without mammalian predators. Fossils of early flying paleognaths in North America and flightless ratites in Europe and the lack of early fossils in the southern hemisphere support a Laurian rather than Gondwanaland origin of the group. This would be similar to the Marsupials which reached Gondwanaland and thence Australia via South America leaving the American Marsupials such as the Opossums in their wake.
So, I’ll leave it with you. If you wish to pursue it, I suggest you study these excellent Wikipedia articles: Palaeognathae and Ratites, from which I got much of information here including the cladogram. I like the idea of unsolved mysteries offered by the natural world to put the all-seeing and all-knowing Homo sapiens in its place, maybe a subtle Gaia’s revenge.

Ian Montgomery,
454 Forestry Road, Bluewater, Qld 4818
Phone: 0411 602 737 +61-411 602 737
Preferred Email: ian@birdway.com.au

Recorder Society http://www.nqrs.org.au

Lee’s Addition:

I enclosed all of Ian’s newsletter, BUT!! As my readers know, this blog is written from a Christian Perspective, and we include articles about birds from various authors. I am a Creationist and do not believe in evolution.
“In the beginning God created the heavens and the earth.” (Genesis 1:1 NKJV)
“Then God said, “Let the waters abound with an abundance of living creatures, and let birds fly above the earth across the face of the firmament of the heavens.” So God created great sea creatures and every living thing that moves, with which the waters abounded, according to their kind, and every winged bird according to its kind. And God saw that it was good. And God blessed them, saying, “Be fruitful and multiply, and fill the waters in the seas, and let birds multiply on the earth.” So the evening and the morning were the fifth day.” (Genesis 1:20-23 NKJV)
So, these Ratites most likely developed along the lines that Ian described, which is why I am posting this. Yet, I disagree with the timeline. Most likely the flood greatly affected those first members of the families.
“Then God spoke to Noah, saying, “Go out of the ark, you and your wife, and your sons and your sons’ wives with you. Bring out with you every living thing of all flesh that is with you: birds and cattle and every creeping thing that creeps on the earth, so that they may abound on the earth, and be fruitful and multiply on the earth.” So Noah went out, and his sons and his wife and his sons’ wives with him. Every animal, every creeping thing, every bird, and whatever creeps on the earth, according to their families, went out of the ark.” (Genesis 8:15-19 NKJV)
Let the Word speak for itself, and realize that these birds did branch out as described, but minus the lengthy timeline. Ian did a great job of explaining all of the very interesting ratites.

Bald – Golden – Steller’s Sea – Eagles Compared

Steller’s Sea Eagle (Haliaeetus pelagicus) next to Bald Eagle by Lee at National Aviary

“Wilt thou set thine eyes upon that which is not? for riches certainly make themselves wings; they fly away as an eagle toward heaven.” (Proverbs 23:5 KJV)

The last post mentioned the Golden Eagle and the Sea Eagle. We were privileged to have seen the Bald Eagle [almost daily here in Polk Country this time of the year.], the Golden Eagle, and the Steller’s Sea Eagle. Just thought you might like a size comparison. The above photo was taken at the National Aviary in Pittsburgh, PA. The two exhibits were side by side and I was overwhelmed at the size of the Steller’s Sea Eagle on the right, and the Bald Eagle on the left. I backed up so I could get them both. What a difference!

Bald Eagle (Haliaeetus leucocephalus) by Lee at National Aviary

Bald Eagle (Haliaeetus leucocephalus) by Lee at National Aviary

The Bald Eagle has a body length of 70–102 cm (28–40 in). Typical wingspan is between 1.8 and 2.3 m (5.9 and 7.5 ft) and mass is normally between 3 and 6.3 kg (6.6 and 13.9 lb).[5] Females are about 25% larger than males, averaging 5.6 kg (12 lb), and against the males’ average weight of 4.1 kg (9.0 lb)

Golden Eagle (Aquila chrysaetos) Flying ©WikiC

The Golden Eagle is a very large raptor, 66 to 102 centimetres (26 to 40 in) in length. Its wings are broad and the wingspan is 1.8 to 2.34 metres (5 ft 11 in to 7 ft 8 in). Golden eagles’ wingspan is the fifth largest among living eagle species. Females are larger than males, with a bigger difference in larger subspecies. Females of the large Himalayan golden eagles are about 37% heavier than males and have nearly 9% longer wings, whereas in the smaller Japanese golden eagles, females are only 26% heavier with around 6% longer wings.[2][8] In the largest subspecies (A. c. daphanea), males and females weigh typically 4.05 kilograms (8.9 lb) and 6.35 kg (14.0 lb), respectively. In the smallest subspecies, A. c. japonica, males weigh 2.5 kg (5.5 lb) and females 3.25 kg (7.2 lb).[2] In the species overall, males average around 3.6 kg (7.9 lb) and females around 5.1 kg (11 lb). The maximum size of golden eagles debated. Large subspecies are the heaviest representatives of the Aquila genus and this species is on average the seventh-heaviest living eagle species. The golden eagle is the second heaviest breeding eagle in North America, Europe and Africa and the fourth heaviest in Asia. For some time, the largest known mass authenticated for a wild female was the specimen from the A. c. chrysaetos subspecies which weighed around 6.7 kg (15 lb) and spanned 2.55 m (8 ft 4 in) across the wings.[10] American golden eagles are typically somewhat smaller than the large Eurasian species,

Steller’s Sea Eagle (Haliaeetus pelagicus) by Lee at National Aviary

Steller’s Sea Eagle (Haliaeetus pelagicus) Feet by Lee at National Aviary

Steller’s sea eagle is the largest bird in the genus Haliaeetus and is one of the largest raptors overall. Females vary in weight from 6,195 to 9,500 g (13.658 to 20.944 lb), while males being rather lighter with a weight range of 4,900 to 6,800 g (10.8 to 15.0 lb). The average weight is variable, possibly due to seasonal variation in food access or general condition of eagles, but has been reported as high as a mean mass of 7,757 g (17.101 lb) to a median estimate weight of 6,250 g (13.78 lb)… [Above from Wikipedia, with editing.]

Steller’s Sea-eagle at San Diego Zoo 2015 by Lee


Golden Eagles in Scotland – YouTube

Birds of the Bible – Eagles